ITS launch vehicle

This article is about an abandoned design for an interplanetary launch vehicle and spaceship. For the currently in-development successor design, see BFR (rocket). For the Mars mission architecture being advanced by SpaceX, see SpaceX Mars transportation infrastructure.

The second stage of the Earth launch vehicle was planned to have two versions, the Interplanetary spaceship for passengers and cargo and the ITS tanker to deliver propellants to Earth orbit. Both were to be powered by six vacuum-optimized Raptor rocket engines with three additional sea-level-nozzle Raptor engines for maneuvering. Thus, the element of the launch vehicle that was to provide second-stage acceleration to orbital velocity on all launches from Earth would also be used as an on-orbit spacecraft. The Interplanetary spaceship was planned as a very long-duration carrier of both passengers and space cargo to interplanetary destinations, and was to have served as both a descent and ascent vehicle at Mars.

The high-level specifications for the vehicle were publicly announced in September 2016, but by July 2017, SpaceX had stated they would not build the 12 m (39 ft)-diameter vehicles as previously planned, but would instead build a "still large" but much smaller launch vehicle first.[4] Subsequently, that was revealed to be the BFR in September 2017, a vehicle intended to cost-effectively replace and supersede all existing SpaceX launch vehicles and passenger/cargo spacecraft.[5][6]

As early as 2007 however, Musk had stated a personal goal of eventually enabling human exploration and settlement of Mars.[9][10]
Bits of additional information about the mission architecture were released in 2011–2015, including a 2014 statement that initial colonists would arrive at Mars no earlier than the middle of the 2020s,[7] and SpaceX began development of the large Raptor rocket engine for the Mars Colonial Transporter before 2014.

Musk stated in a 2011 interview that he hoped to send humans to Mars' surface within 10–20 years,[10] and in late 2012 that he envisioned the first colonists arriving no earlier than the middle of the 2020s.[7][11][12]

In October 2012, Musk first publicly articulated a high-level plan to build a second reusable rocket system with capabilities substantially beyond the Falcon 9/Falcon Heavy launch vehicles on which SpaceX had by then spent several billion US dollars.[13] This new vehicle was to be "an evolution of SpaceX's Falcon 9 booster ... much bigger [than Falcon 9]." But Musk indicated that SpaceX would not be speaking publicly about it until 2013.[7][14]
In June 2013, Musk stated that he intended to hold off any potential IPO of SpaceX shares on the stock market until after the "Mars Colonial Transporter is flying regularly."[15][16]

In February 2014, the principal payload for the MCT launch vehicle was announced to be a large interplanetary spacecraft named Mars Colonial Transporter, capable of carrying up to 100 tonnes (220,000 lb) of passengers and cargo.[17] Musk stated that Mars Colonial Transporter will be "100 times the size of an SUV".[18]
According to SpaceX engine development head Tom Mueller, concept designs at the time indicated SpaceX could use nine Raptor engines on a single rocket, similar to the use of nine Merlin engines on each Falcon 9 booster core, in order "to put over 100 tons of cargo on Mars."[18]
At that time, it appeared that the large rocket core that would be used for the booster to be used with MCT would be at least 10 meters (33 ft) in diameter—nearly three times the diameter and over seven times the cross-sectional area of the Falcon 9 booster cores—and was expected to have up to three rocket cores with a total of at least 27 engines.[8]

By August 2014, media sources speculated that the initial flight test of the Raptor-driven super-heavy launch vehicle could occur as early as 2020, in order to fully test the engines under orbital spaceflight conditions; however, any colonization effort was then reported to continue to be "deep into the future".[19][20]

Rendering of an ITS on ascent

Previously, the launch vehicle was known informally as the BFR ("Big Falcon Rocket or Big Fucking Rocket"),[21] a name coined by Musk personally in reference to the BFG 9000 from the 1993 video game Doom.[17][22][23]

The spacecraft had a similar moniker: informally dubbed the BFS (for Big Fucking Spaceship), also coined by Musk.[17]

SpaceX indicated in 2014 that there may be more than one design in a family of SpaceX super-heavy lift launch vehicles.[19]

In January 2015, Musk said that he hoped to release details of the "completely new architecture" for the Mars transport system in late 2015 but those plans changed and, by the end of the year, the plan to publicly release additional specifics had moved to 2016.[17][24]

Musk stated in June 2016 that the first unmanned MCT Mars flight could happen as early as for 2022, to be followed by the first manned MCT Mars flight departing as early as 2024.[25][26]
Company plans as of mid-2016 continued to call for the arrival of the first humans on Mars no earlier than 2025.[25]
As of 25 August 2016, the rocket had not yet been given a formal name by SpaceX, although Musk commented on a proposal on Twitter to name it "Millennium".[27] In his September 2016 announcement, Musk referred to the vehicle components as the "interplanetary booster", the "interplanetary spaceship", and the "tanker".
In mid-September 2016, Musk noted that the Mars Colonial Transporter name would not continue, as the system would be able to "go well beyond Mars", and that a new name would be needed. The name selected was Interplanetary Transport System (ITS)[28]

Artist's concept of the ITS Interplanetary Spaceship, landed on Saturn's moon Enceladus.

SpaceX CEO Musk unveiled details of the space mission architecture, launch vehicle, spacecraft, and Raptor engines that power the vehicles at the 67th International Astronautical Congress on September 27, 2016. The first firing of a Raptor engine occurred on a test stand in September 2016 as well.[29][30]

In October 2016, Musk indicated that the initial prepreg carbon-fiber tank test article, built with no sealing liner, had performed well in initial cryogenic fluid testing, and that a pressure test of the tank at approximately 2/3 of the design burst pressure was slated for later in 2016, with the very large tank placed on an ocean barge for the test.[31] This test was successfully completed in November 2016.[32]

In July 2017, SpaceX made public plans to build a much smaller launch vehicle and spacecraft prior to building the ITS, and stated that the new system architecture had "evolved quite a bit" since the November 2016 articulation of the very large ITS launch vehicle. A key driver of the new architecture is to make the new system useful for substantial Earth-orbit and cislunar launches so that the new system might pay for itself, in part, through commercial spaceflight activities in the near-Earth space zone.[4][6]
In September 2017, the new smaller design was revealed to be the 9 m (30 ft) diameter launch vehicle, referred to by its "code name" BFR, with similar core vehicle structure (carbon fiber), engines (Raptor), and Mars mission architecture;[6][33] but explicitly aimed at superseding and replacing the entire existing set of SpaceX launch vehicle and spacecraft offerings—Falcon 9, Falcon Heavy, and the Dragon spacecraft—with a more cost-effective LV, while being designed to be fully reusable like the ITS launch vehicle.[5]

The ITS launch vehicle stack is composed of two stages. The first stage is always an interplanetary booster while the second stage may be either an interplanetary spaceship (for beyond-Earth-orbit missions) or an ITS tanker (for on-orbit propellant transfer operations).

The overall launch vehicle height, first stage and the integrated second-stage/spacecraft, will be 122 m (400 ft).[37] Both stages of the ITS LV will be constructed of lightweight-yet-strong carbon fiber, even the deep-cryogenic propellant tanks, a major change from the aluminum-lithium alloy tank and structure material used in SpaceX Falcon 9 family of launch vehicles. Both stages are fully reusable and will land vertically, technology initially developed on the Falcon 9 launch vehicle first stages in 2012–2016.[35][36]
Gross liftoff mass is 10,500 tonnes (23,100,000 lb) at a lift-off thrust of 128 meganewtons (29,000,000 lbf). ITS LV would be able to carry a payload to low-Earth orbit of 550 tonnes (1,210,000 lb) in expendable-mode and 300 tonnes (660,000 lb) in reusable mode.[3]

The engine configuration will include 21 engines in the outer ring and 14 in the inner ring, with these 35 engines fixed in place. The center cluster of seven engines are gimbaled for directional control, although some directional control to the rocket is also available by utilizing differential thrust on the fixed engines. Design thrust on each engine is variable between 20 and 100 percent of rated thrust.[36]

Methane/oxygen will also be used to power the control thrusters, as gas thrusters rather than the subcooled liquid used to power the main engines. The methalox control thrusters will be used to control booster orientation in space, as well as to help provide additional accuracy in landing once the velocity of the descending booster has slowed.[36]

The design is intended to use about seven percent of the total propellant load at launch in order to support the reusable aspect and bring the booster back to the launch pad for a vertical landing, assessment, and relaunch,[36]
assuming a separation velocity of approximately 8,650 km/h (2.40 km/s).[38]
During atmospheric reentry, once the atmosphere is sufficiently dense, grid fins will be used to control the attitude of the rocket and fine tune the landing location.[36]
The booster return flights are expected to encounter loads that are lower than those experienced on the Falcon 9 rentries, principally because it will have both a lower mass ratio and a lower density than Falcon 9.[31]
The booster will be designed for 20 G nominal loads, and possibly as high as 30–40 G's without breaking up.[31]

In contrast to the landing approach used on SpaceX mid-2010s reusable rocket first stages—either a large, flat concrete pad or downrangefloating landing platform used with Falcon 9 and Falcon Heavy—the ITS booster was to be designed to land on a launch mount itself, where it may then be refilled with propellant and checked out for follow-on flights.[36]

The ITS launch vehicle does not have a dedicated and single-function second stage in the way most launch vehicles have had. Instead, the upper stage function of gaining sufficient velocity to place a payload into Earth orbit is provided as a relatively short term role by a spacecraft that has all the requisite systems for long-duration spaceflight.[36] This is not a role that most upper stages have had in launch vehicle designs through the 2010s, as typical upper stage on-orbit life is measured in hours.
Previous exceptions to this norm exist, for example the Space Shuttle orbiter provided part of the boost energy and all of the second stage energy for lofting itself into low-Earth orbit. Differences also exist: the Space Shuttle expended its propellant tank and primary launch vehicle structure on ascent, whereas the ITS first- and second-stage options are designed to be fully reusable.

In the 2016 design, SpaceX had identified two spacecraft that would also play the upper stage role on each Earth-away launch: the interplanetary spaceship and the ITS tanker.
Both spacecraft are the same physical external dimensions: 49.5 m (162 ft)-long and 12 m (39 ft)-diameter 17 m (56 ft) across at the widest point. Both designs were powered by six vacuum-optimized Raptor engines, each producing 3.5 MN (790,000 lbf) thrust, and were to have had three lower-expansion-ratio Raptor engines for in-space maneuvering as well as during descent and landing to allow for reuse on future launches.[35][3]

The Interplanetary spaceship was a large passenger-carrying spacecraft design proposed by SpaceX as part of their ITS launch vehicle in September 2016. The ship would operate as a second-stage of the orbital launch vehicle on Earth-ascents—and would also be the interplanetarytransport vehicle for both cargo and passengers— capable of transporting up to 450 tonnes (990,000 lb) of cargo per trip to Mars following propellant-refill in Earth orbit.[35]

Back-quarter view of a rendering of the interplanetary spaceship from engineering drawings, with the solar panels extended.

In addition to use during maneuvering, descent and landing, the three lower-expansion-ratio Raptor engines were also to have been used for initial ascent from the surface of Mars.[35]
In 2016, the first test launch of a spaceship was not expected until 2020 or later, and the first flight of the ITS booster was expected to follow a year or more later.[1]

Rendering of an ITS tanker (top) transferring propellant to an interplanetary spaceship (bottom) in Earth orbit.

Early Mars flights—in the mid-2020s or later—were expected to carry mostly equipment and few people.[7]

The ITS tanker is a propellant tanker variant of the ITS second stage spacecraft. This spacecraft design was to be used exclusively for launch and short-term holding of propellants to be transported to low-Earth orbit. Once on orbit, a rendezvous operation was to have been effected with one of the interplanetary spaceships, plumbing connections made, while a maximum of 380 tonnes (840,000 lb) of liquid methane and liquid oxygen propellants would be transferred in one load to the spaceship. To fully fuel an interplanetary spaceship for a long-duration interplanetary flight, it was expected that up to five tankers would be required to launch from Earth, carrying and transferring a total of nearly 1,900 tonnes (4,200,000 lb) of propellant to fully load the spaceship for the journey.[3][36]

Following completion of the on-orbit propellant offloading, the reusable tanker was to reenter the Earth's atmosphere, land, and be prepared for another tanker flight.[3]

Importantly, the "fully and rapidly reusable" aspect of the ITS launch vehicle and spacecraft design was the largest factor in the SpaceX analysis for bringing down the currently huge cost of transporting mass to space, in general, and to interplanetary destinations, in particular. While the transport system under development in 2016-2017 relied on a combination of several elements to make long-duration beyond Earth orbit (BEO) spaceflights possible by reducing the cost per ton delivered to Mars, the reusability aspect of the launch and spacecraft vehicles alone was expected by SpaceX to reduce that cost by approximately 2 1/2orders of magnitude over what NASA had previously achieved on similar missions. Musk stated that this is over half of the total 4 1/2 orders of magnitude reduction that he believes is needed to enable a sustainable settlement off Earth to emerge.[39][3]

When announced in September 2016, the targeted location for initial launches of the ITS launch vehicle was LC-39A, at SpaceX's leased pad at Launch pad 39A on the Floridacoast, the same launchpad where Apollo 11 launched in 1969 to the Moon. Subsequent Apollo Missions were also launched from the pad.[35]

The concept of operations for ITS launches envisioned the fully loaded second-stage reaching orbit with only minimal propellant remaining in the interplanetary spaceship vehicle's tanks. Then, while the spaceship remained in Earth orbit, three to five cargo second stages—called ITS tankers—would be launched from Earth carrying additional methane fuel and liquid oxygen oxidizer to rendezvous with, and transfer propellant to, the outgoing spaceship. Once refueled, the spaceship was to perform a trans-Mars injection burn, departing Earth orbit for the interplanetary portion of the journey.[35]

The development work on the new two-stage launch vehicle design was privately funded by SpaceX. The entire project is even possible only as a result of SpaceX multi-faceted approach focusing on the reduction of launch costs.[35]

Blue Origin's New Glenn rocket, announced in September 2016, is also expected to compete in the super-heavy lift class.[41] In March 2017, New Glenn's reusable payload capacity was announced as 45 tonnes to LEO and 13 tonnes to GTO.[42]

^ abcFoust, Jeff (2016-09-27). "SpaceX's Mars plans call for massive 42-engine reusable rocket". SpaceNews. Retrieved 2016-10-14. Musk stated it’s possible that the first spaceship would be ready for tests in four years, with the booster ready a few years after that, but he shied away from exact schedules in his presentation. 'We’re kind of being intentionally fuzzy about the timeline,' he said. 'We’re going to try and make as much progress as we can with a very constrained budget.'

^ abcElon Musk (19 July 2017). Elon Musk, ISS R&D Conference (video). ISS R&D Conference, Washington DC, USA. Event occurs at 49:48–51:35. Retrieved 21 September 2017. the updated version of the Mars architecture: Because it has evolved quite a bit since that last talk. ... The key thing that I figured out is how do you pay for it? if we downsize the Mars vehicle, make it capable of doing Earth-orbit activity as well as Mars activity, maybe we can pay for it by using it for Earth-orbit activity. That is one of the key elements in the new architecture. It is similar to what was shown at IAC, but a little bit smaller. Still big, but this one has a shot at being real on the economic front.

^Boyle, Alan (5 January 2015). "Coming Soon From SpaceX's Elon Musk: How to Move to Mars". NBC News. Retrieved 2016-09-25. The Mars transport system will be a completely new architecture. Am hoping to present that towards the end of this year. Good thing we didn't do it sooner, as we have learned a huge amount from Falcon and Dragon.

^ ab"KSC meeting portrays SLS as scrambling for a manifest plan". 12 January 2016. Retrieved 14 January 2016. Also notable – though understandably not referenced at the KSC meeting – is SpaceX’s plan to have its BFR – a reusable booster with the power of two Saturn Vs – already up and running by the 2020s, ahead of MCT (Mars Colonial Transporter) missions.

^2016 StartmeupHK Venture Forum - Elon Musk on Entrepreneurship and Innovation. StartmeupHK Venture Forum--2016. via InvestHK YouTube channel: Invest Hong Kong. 26 January 2016. Retrieved 28 January 2016. (SpaceX discussion at 30:15-31:40) We'll have the next generation rocket and spacecraft, beyond the Falcon and Dragon series ... I'm hoping to describe that architecture later this year at the International Astronautical Congress. which is the big international space event every year. ... first flights to Mars? we're hoping to do that in around 2025 ... nine years from now or thereabouts.

^Elon Musk (27 September 2016). Making Humans a Multiplanetary Species (video). IAC67, Guadalajara, Mexico: SpaceX. Event occurs at 9:20–10:10. Retrieved 10 October 2016. So it is a bit tricky. Because we have to figure out how to improve the cost of the trips to Mars by five million percent ... translates to an improvement of approximately 4 1/2 orders of magnitude. These are the key elements that are needed in order to achieve a 4 1/2 order of magnitude improvement. Most of the improvement would come from full reusability—somewhere between 2 and 2 1/2 orders of magnitude—and then the other 2 orders of magnitude would come from refilling in orbit, propellant production on Mars, and choosing the right propellant.